In the operation of any internal combustion engine, the practice of recycling a certain amount of exhaust gas from the exhaust, to the engine intake manifold is well known. Such a practice is found to be effective toward reducing the amount of harmful constituents which would otherwise be discharged into the atmosphere. Further, the gas recycling procedure can be practiced in a manner to not substantially interfere with the efficiency of the engine.
Normally, in a premixed or carbureted charge to an engine, the rate of exhaust gas recycling is controlled by the degree of vacuum which exists in the engine intake manifold. It could, however, be responsive to the vacuum established at another point that is subject to a varying vacuum condition in response to engine load and speed.
In the instance of a fuel injection engine of the type presently considered, a relatively constant air charge is introduced to each combustion chamber. Over the range of operation, there will be no vacuum variations indicative of the engine's immediate operating condition. To properly vary the exhaust gas recycling rate then, means must be provided to in effect establish an artificial vacuum condition. The latter can then be modified in response to the engine's speed and load condition.
In the instant arrangement, a fuel injection engine of the type contemplated is provided, with a valve member for varying the volume of exhaust gas flow from the engine exhaust conduit, to the air intake manifold. This valve member is subject to adjustment for altering said gas flow, in a manner that is determined by the degree of vacuum imposed on an exhaust gas flow controller. The vacuum condition is in turn varied in response to the physical adjustment of an air bleed orifice which leaks air into the vacuum system. The orifice is provided with an adjustable constricted opening which functions to permit a certain amount of air to leak into the vacuum system, thereby to in effect alter the setting of the exhaust gas flow controller.
It is therefore an object of the invention to provide an exhaust gas recycling loop or cycle for an internal combustion engine. A further object is to provide an exhaust gas recycling system in an engine which is adapted to operate on the fuel injection principle wherein no substantial degree of vacuum is achieved in the intake manifold, which might be utilized as the control medium.
Another object is to provide a method for efficiently circulating an amount of internal combustion exhaust gas as to more effectively adjust flow of the latter.
Toward overcoming the above stated problems, and toward achieving the enumerated objectives, the applicant has provided a method which utilizes an adjustable flow exhaust gas recirculating system. The latter is capable of passing a flow of hot exhaust gas from the engine's exhaust carrying conduit to a point where it will mix with air which is introduced to the various combustion chambers.
To power the system, a constant source of vacuum is provided in the form of a vacuum pump or other vacuum establishing element which is normally driven by the engine. Since the degree of vacuum imposed on the exhaust gas controller will regulate the exhaust gas flow, the magnitude of the vacuum is adjusted by bleeding air into the system through an adjustable orifice. Said orifice comprises an adjustable unit having a venting arrangement such that air might pass through the unit's constricted portion and into the vacuum segment of the system.
The adjustable orifice or air bleed valve is automatically regulated to provide the necessary degree of air bleed in response to the disposition of the engine fuel pump. The latter is provided with an operable element capable of affording an indication of the fuel flow to each combustion chamber. The fuel pump is further provided with means to monitor the speed of the engine. These two sources of information, or signals corresponding thereto, are transmitted to the adjustable orifice in the form of dual responses whereby to effect the proper orifice adjustment.